Smoking a pack a day causes 150 mutations in every lung cell shows research

November 4, 2016

Genetic mutations in the DNA of a cell are known to be a cause of cancer
US researchers also discovered damage in the bladder, liver and throat
Experts say the findings explain the risk of forms of cancer from smoking

Stephen Matthews For Mailonline

Published:
14:00 EDT, 3 November 2016

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Updated:
05:34 EDT, 4 November 2016

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Smoking a pack a day of cigarettes can cause 150 damaging changes to a smoker’s lung cells each year, scientists claim.

Mutations in the DNA of a cell are known to cause cancer and could explain why smokers are at such high risk of the disease in their lung.

But experts discovered a whole host of mutations caused by tobacco throughout various organs in the body.

Despite the lungs being the primary location, the bladder, liver and throat also suffered smoking-related damage – possibly explaining the risk of other forms of cancer.

Experts found a whole host of mutations caused by tobacco throughout organs in the body

The habit kills six million people a year worldwide and, if current trends continue, the World Health Organization predicts more than 1 billion tobacco-related deaths this century.

Smoking has been linked with at least 17 types of cancer, but until now scientists were not clear on the mechanisms behind many of them.

The study conducted by US researchers analysed over 5,000 tumours, comparing cancers from smokers with those from people who had never smoked.

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It found certain molecular fingerprints of DNA damage – called mutational signatures – in the smokers’ DNA, and the scientists counted how many of these were in different tumours.

In lung cells, they found that on average, smoking a pack of cigarettes a day led to 150 mutations in each cell every year.

The results also showed that a smoking a pack of cigarettes a day led to an average 97 mutations in each cell in the larynx, 39 mutations for the pharynx, 23 for the mouth, 18 for the bladder, and six mutations in every cell of the liver each year.

A metastatic melanoma of the lungs: In lung cells, researchers found that on average, smoking a pack of cigarettes a day led to 150 mutations in each cell every year

Each mutation is a potential start point for a ‘cascade of genetic damage’ that can eventually lead to cancer, they said.

They said the findings show a direct link between the number of cigarettes smoked in a lifetime and the number of mutations in the DNA of cancerous tumours.

Study author Ludmil Alexandrov, from the Los Alamos National Laboratory, said that it had until now been difficult to explain how smoking increases the risk of cancer in parts of the body that don’t come into direct contact with smoke.

SIX MILLION DEATHS

Smoking kills six million people a year worldwide and, if current trends continue, the World Health Organization predicts more than 1 billion tobacco-related deaths this century.

‘Before now, we had a large body of epidemiological evidence linking smoking with cancer, but now we can actually observe and quantify the molecular changes in the DNA,’ he added.

Mike Stratton, who co-led the work at Britain’s Wellcome Trust Sanger Institute, said it was a bit like digging in to the archaeology of each tumour.

‘The genome of every cancer provides a kind of archaeological record, written in the DNA code itself, of the exposures that caused the mutations,’ he said.

‘Looking in the DNA of cancers can provide provocative new clues to how [they] develop and thus, potentially, how they can be prevented.’

The study was published in the journal Science on Thursday.